Method of making a hot melt pressure-sensitive adhesive

Abstract

A method of making a pressure-sensitive hot melt adhesive. The method includes extruding a melt composition that includes a polymer, wherein the polymer has acidic groups covalently attached thereto, and a metal salt hydrate, wherein the metal salt hydrate has a melting point that is less than the maximum processing temperature.

What is claimed is: 
     
       1. A method of making a hot melt pressure-sensitive adhesive composition, the method comprising melt compounding, at or below a maximum processing temperature, components comprising:
 an acidic polymer; and 
 a metal salt hydrate, wherein the metal salt hydrate has a melting point that is less than the maximum processing temperature, and further wherein the melt compounding is conducted by high shear mixing. 
 
     
     
       2. The method of  claim 1 , wherein the components further comprise a tackifier. 
     
     
       3. The method of  claim 1 , wherein the polymer comprises an acrylic polymer. 
     
     
       4. The method of  claim 1 , wherein acidic groups of the acidic polymer comprise at least one of carboxyl groups, phosphono groups, sulfo groups, and combinations thereof. 
     
     
       5. The method of  claim 1 , wherein acidic groups of the acidic polymer comprise carboxyl groups. 
     
     
       6. The method of  claim 1 , wherein the metal salt hydrate comprises an alkaline earth metal. 
     
     
       7. The method of  claim 1 , wherein the metal salt hydrate comprises magnesium acetate tetrahydrate. 
     
     
       8. The method of  claim 1 , wherein the metal salt hydrate comprises an alkali metal. 
     
     
       9. The method of  claim 1 , wherein the metal salt hydrate comprises a transition metal. 
     
     
       10. The method of  claim 1 , wherein the metal salt hydrate comprises a Group 13 metal. 
     
     
       11. The method of  claim 1 , wherein the metal salt hydrate has a melting point in a range of from 30° C. to 170° C. 
     
     
       12. The method of  claim 1 , wherein the components further comprise a blend compatible diluent polymer. 
     
     
       13. The method of  claim 1 , wherein the components are essentially free of volatile organic solvents. 
     
     
       14. The method of  claim 1 , wherein the metal salt hydrate comprises a crystalline metal salt hydrate.